Production of fuel oils and naphthenic acid soaps



Oct. 20, 1953 TURNER 2,656,380

PRODUCTION OF FUEL OILS AND NAPHTHENIC ACID SOAPS Filed NOV. 29 1949 CAUSTIC 51 3mm. 4 i 6 STORAGE 7Q- +|m 5 WASHER I 2 3 0 PRODUCT v Q J TANK SURGE TANK l7 4 l5 37 ml "4 5 H) Y ngrrl IIJ i 48- Q l 49 (I m LLLLLLL 5| B a S INVENTOR 52 Cyril R. Turner Patented Oct. 20, 1953 PRODUCTION OF FUEL OILS AND NAPHTHENIC ACID SOAPS Cyril R. Turner, Lafayette, Calif., assignor, by mesne assignments, to California Research Corporation, San Francisco, Calif., a corporation of Delaware Application November 29, 1949, Serial No. 129,938

This invention relates to a process of producing naphthenic acids and petroleum hydrocarbons, or, more particularly, to an improved method of producing naphthenic acids in the form of naphthenic soap and naphthenic-soap-free hydrocarbons from naphthenic-soap-containing petroleum hydrocarbon fractions.

Various crude oils are known to contain minor amounts of naphthenic acids. In order to recover naphthenic acids, it is a common practice to wash the crude oils or petroleum fractions where the naphthenic acids concentrate with an aqueous caustic soda solution in order to separate naphthenic acids in the form of soap from the hydrocarbons. Thereafter, the soap which is soluble in the aqueous caustic solution is separated from the hydrocarbons and this caustic solution may be acidified to recover the soaps in the form of naphthenic acids. The recovery of naphthenic acids has become more and more important as new uses for the acids and their salts have been found. I

Naphthenic acids and their salts are used in 3 Claims. (CL 260-514) soap in order to meet the specifications. The

acid-treating process has been found to be very expensive because of the high maintenance and special handling cost. 1

It is an object of this invention to provide a method of recovering naphthenic acids in the vform of soap and naphthenic-soap free hydrocarbons from petroleum hydrocarbons.

It is another object of this invention to provide a method of economically recovering naphthenic acids in the form of soap and separating minor amounts of naphthenic soaps from caustictreated petroleum hydrocarbons.

It is still another object of this invention to provide a method of obtaining an alkali-treated petroleum hydrocarbon free of naphthenic soaps.

preparing drying oil compositions for paints, dc-

tergents, and for making various fungicidal compositions, etc. The caustic washing of the crude oil or petroleum fractions converts the naphthenic acids to naphthenic soaps and extracts substantially all of the acid from the petroleum hydrocarbons. However, the known processes do not remove all of the naphthenic soaps from the oil. Though the amount of naphthenic soaps remaining in the crude petroleum or petroleum fractions after the caustic treatment do nothave harmful effects in many of the applications towhich the petroleum products are put, these minor amounts of soap have been found to be especially undesirable when the products are used as fuels. This is particularly noticeable when the caustic-- treated gas oils are used in diesel fuels. It has been found that the small amounts of soap in diesel fuel oils result in injector plugging and filter plugging, etc. Likewise, when the gas oils are used as fuels for domestic burners, plugging of the fuel lines often occurs. In order to overcome this difficulty, many refiners have established a maximum soap content in their specifications for diesel and burner fuels. Thecaustictreated petroleum fractions are commonly washed It is a further object to recover naphthenic acids in the form of soap from naphthenic-acid containing petroleum hydrocarbons and to produce naphthenic-soap free petroleum hydrocarbons.

rhese and still further objects of the present invention will be apparent from the following description.

It has been discovered that fuel oils and naphthenic acids in a form of soap can be produced from naphthenic-acid containing'petroleum fractions by a process comprising treating the hydrocarbons with an aqueous alkali solution which converts the naphthenic acids to naphthenic soaps, separating an aqueous alkali phase containing substantially all of the soap from the hydrocarbon phase, treating the hydrocarbon phase with an aqueous solution of a non-cationic watersoluble, surface-active agent, and separating an aqueous phase containing said soap from a hydro carbon phase free of said soap.

As used herein and in the appended claims, the term soap number is used to express the amount of naphthenic soap present in the hydrocarbons. This term represents the number of milligrams of potassium hydroxide per gram of sample equivalentto the naphthenic soaps in the petroleum. A measured amount of acid is agitated with a measured amount of hydrocarbons and the mixture is titrated with a potassium hydroxide solution to the methyl-orange .end

point. The soap number is calculated in the folwith dilute sulfuric acid to remove or destroy lowing manner:v

(M1. acid normality M1. ,KOH X normality (for back titration) Xmol. wt; .of K OH) -Ml. of samplcXspecific gravity of sample. w

circulation of the caustic.

\d When nitrogen bases are present in the hydrocarbons being analyzed, the amount of nitrogen bases must be determined and subtracted from the above soap determination in order to ascertain accurately the amount of soap present.

In order to describe the invention in more detail, reference will now be made to the appended schematic flow diagram.

Referring to the appended diagram in which suitable apparatus is shown for practicing the process of this invention, a gas oil boiling in the range of 375-685 F. and having a naphthenicacid content of 1.5 weight per cent 13cm stor age tank I is withdrawn through line 2 and passes into pump 3 which forces the hi1 through line 4 into washer I. x m

An 8 Baum caustic sciuu'cu held in caustic storage 5 is withdrawn through line 6 and passes into washer 1. Caustic or foth'e'r. alkalisolutions from 1 to about 10 Baum may be used and the feed and surface-active solution. Heating generally lowersthe viscosity of the feed oil so that peueqniixmg of the surface-active agent and feed and better separation of the oil and aqueous phases can be obtained. Therefore, when the feed to be treated has a sufiiciently low viscosity heating may not be necessary. However, when a brightening step is to be included in the process, theresultingmixture of aqueous surfaceamount of solution, however, depends uteri the" quantity of naphthenic acids present in the oil. The caustic solution or 'oil 'caustic mixture passes cut or line a into um 9 which forces the caustic solution or caustic-oil mixture into line 4 through line 10. This mixture passes through a mixing zone H where the caustic and feed oil are mixed. pump 9 is not always necessary to obtain the In many instances a venturi may be employed. The mixing zone H may comprise a bailied line or other suitable mixing device's. Feed oil is withdrawn from storage tank I until the 'free caustic present in the washer 1 is in the range of about 4 to 10 pounds per 100 gallons of oil.

The addition of caustic solution to the naphthenica'ci'd containing feed oil converts the naphthenic acids to sodium naphth'enates which separates along with the aqueous caustic solution from the hydrocarbons in a phase separation and passes out through line i3 into product tank 14.

as it is called, thereafter is generally separated from the free caustic and water.

Treated oil passes out line l2 into settler and surge tank l5. Entrained aqueous caustic solu- The sodium naphthenate or naphthenate soap,

tion and naphthenic soapssettle and pass out line [6 into line l3 and theninto product tank 14.

The oil from. settler. l5 passes out line I1 and then into pump l8 whichuiorces the oil through line I]; .The oil. inline "was found to have a soap content of 0.031 soap nun ber Irssh Wa enf line!! nas 'eaim whi h d re tly e e ii enlb we l I ma b a edb' any 1 b 1 1 An alkyl aromatic si'llfc inate, a surracc i" cant having an "average 'mciccuia'r weight r about 350 added at a sa for about 030042 pound 'per gallon or water to ho't wellfll through line 23. The aqueous sulfonate solution is pumpeqcut of not well 21 through 1m 24 by pump H) which "forces the solution through 2t. A portion of the as ects suifonate solution passes from line 26 through valved 'line 21, wherein valve to the surface-active solution ma vary from i about 1:1 to 20:1 with a ratio of about 10:1 being im stjdel ira la T e dlunie a j' S active solution and feed oil is generally heated to about to 160 F. at this point, with -150 F. being preferred.

The heated mixture in line i9 passes from heater 32 into a mixing zone 33. This mixing zone may comprise a baflled line or other suitable mixing devices. The mixed feed and surfaceactive solution pass into washer tower 29.

The washer tower 29 may be a packed or un"- packed tower of column; The tower packing may be any suitable material such as rock or various other materials or it may be a trayed tower or column.

The oil and aqueous surface-active solutions are separated by phase separation in washer 29 and the aqueous phase containing naphthenic soaps passes out line 35. A stream ofaqueous surface-active solution from line 2-! which passes to washer 29 near the top is added to the washer to prevent entrained surface-active solution containing the naphthenic soaps from passing overhead from washing 29. This stream is not always necessary and, in many instances, it may be preferable touse plain water instead of a surface-active solution. The treated oil phase passes out from washer -29 through -line 36 into settler 39 through line 38 or into line 31. The oil passes into line 38 after valves 4| and 42 are opened and valve 40 is closed. The feed oil passes into line 31 when valve 40 is opened and valves 4| and 42 are closed when the settling step is not necessary. The settling step is used to separate or settle out minor amounts of aqueous phase from the washed oil. When valve 40 is closed and valves 4| and 42 are open, the oil passes into settler 39 wherein a further phase separation of water and oil occurs. The separated water phase containing naphthenic soap in settler "39 passes out of the bottom through line 43 and the treated oil passes out near the top through line 44. Lines 31 and 44 connect to from line 45 wherein oil from "settler 39 or oil directly from washer '29 passes through heater '46 where it is heated to about F. The oil .in this step is generallyheated within about 10 F. of the flash point of the oil in order to obtain the maximum efiiciency in the brightening step. Therefore, depending on the oil being treated, different amounts of heat are added at this point. Heated oil from heater '46 passes through line 41 into brightener 48.

Air, compressed to about 30 ps. i. passes into 'brightener tower or column '48 through line '49. The air needs to be compressed only to a pressuresufficient t o 'in'sure an adequate flow of air at dependent upon the intimacy of contact 75 throughbrigh'tener 48 and it may be pre-heated 11 desired. Brightener as may effect the properties of the oil. bright oil passes out line into product storage be a packed or unpacked tower, that is, similar to washer 29.

The air passes upwards through the downcoming -oil in brightener 48. stripping water vapor and light hydrocarbons from the oil. This step is commonly called a brightening step as minor amounts of water which may cause the oil to appear cloudy are removed. The brightening step is not always necessary when adequate separation is obtained in previous steps or when the small amount of water will not substantially The stripped or tank 52. The stripping air containing water,

vapor and light hydrocarbons passes out of the brightener 48 through line 50.

A soap-number determination conducted on the oil in tank 52 gave a soap number of 0.003.

.The term "non-cationic used in the specification and appended claims is intended to include the water-soluble surface-active agents wherein the surface-active component is either anionic or non-ionic. These surface-active agents or compounds are generally characterized by hydrophobic and hydrophilic groups. The hydrophobic group usually is an organic radical of about 8 to 20 carbon atoms. Polarity and the balance of water-oil affinities and solubilities are imparted by the hydrophobic or by a hydrophilic group. In the anionic surface-active agents the hydrophilic group is an acid or an acid-forming radical attached to the hydrophobic group and is usually utilized in the form of a salt. Thenon-ionic water-soluble surface-active agents are characterized by a surface-active component which does not ionize. Nevertheless, the non-ionic surfacevactive agents contain hydrophobic and hydropolyglycol esters of fatty acids; polyglycol esters of alkyl succinic' acids; polyglycol derivatives of alkyl amines; analogs of the above prepared with propylene oxide; and alkyl polyalkylene-polyamines, etc.

The anionic, water-soluble, surface-active agents which may be used in this invention include the following groups: carboxylic acids and salts, alkane sulfonic acids and salts, alkyl aromatic sulfonic acids and salts, and sulfuric esters. Among the carboxylic acids and salts which may be used in this invention are those having a carboxyl group joined directly to the hydrophobic group. The alkane sulfonic acids and salts include those having a sulfonic group directly linked to the hydrophobic groups, for example, those having no polar substituents, unsubstituted alkane sulfonic acids, and some having somewhat uncertain structural formulae, such as oxidation products of sulfurized olefins, sulfonated resins, etc.; and sulfonic groups joined through an intermediate linkage, such as an ester, amide, ether,

or other miscellaneous linkages having,'for example, two or more linkages. The alkyl aromatic sulfonic acids and salts that may be used in this invention include those wherein the hydrophobic group is joined directly to the sulfonated aromatic nucleus, such as alkyl benzenes, alkyl naphthalenes, alkyl phenols, aromatic condensates, alkyl aromatic ketones, etc.; and those havwater.

aromatic nucleus through anintermediate group,

suchas an ester, amide, or imide, ether,'-etc.

Among the sulfuric esters, or so-called sulfates,

which may be used as a surface-active agent-in this invention, are those having a sulfate group joineddirectly to the hydrophobic group which contains no other polar structures or contains other polar structures, such as sulfonated oil; and those having a sulfate group joined through an intermediate linkage, such as an ester, an amide, or an ether linkage, etc.

Salts of the alkyl aromatic sulfonic acids hav been found to be desirable as a surface-active agent for this invention. It is generally preferred to use the alkyl aromatic sulfonates that have a hydrophobic group joined directly to the sulfonated aromatic nucleus. For example, as illustrated in the following structural formula,

R represents the hydrophobic portion of the molecule I -molecule are especially preferred. The alkyl aryl and alkyl benzene sulfonates may contain more than one side chain or R'gr0up, although molecules containing only one side chain or ,R group are generally preferred. While the'cation portion of the molecule may be composed of various alkali and alkali-earth metals, it generally is preferred to form the salts of these compounds with sodium or potassium. The molecular weight range of the anionic portion of the alkyl aryl sulfonates which may be used as a surface-active agent for this invention varies between about 275 and 450, with those having a molecular weight of about 300 to about-375 being generally preferred.

A mixture of surface-active agents may be used in the surface-active solution of the process of this invention, although it is generally preferred to employ only one agent at a time. The amount of surface-active agent per volume of oil being treated may vary considerably and, in part, depends upon the particular surface-active agent being used and also upon the amount of soap to be removed. For example, in the description of the appended sketch, 0.000042 pound of surfaceactive agent per gallon of oil satisfactorily removed the naphthenic soap from the oil. The maximum amountof surface-active agent depends upon the solubility of the agent in water. However, it is usually preferred to use about 0.3 pound per gallon of the surface-active agent to about as little as 0.00004 pound per gallon of When larger amounts of surface-active agent are used, foaming or emulsifying may occur. Of course, even smaller amounts of this ing a hydrophobic group joined to the sulfonated soap content is relatively high or when the oil to be treated contains a very small amount of soap. The weight per cent of the surface-active agents in an aqueous solution may vary between about 0.0005 to about 0.3 weight per cent with 0.001 to 0.1 being generally preferred.

While a continuous type of process is illustrated in the appended sketch for the soap removal step, a batch-type process is equally feasible.

gas oil and light lubricating oil fractions, it

generally preferred to treat 'disti-llates boiling :in this range or in temperature range of about 325?,F. to about 800 F. It is particularly preiierred to treat diesel duel oils and burner aoils boiling within the range of about 325 F. to-about 725 F. as the soap content is very critical in these fuels.

In order to illustrate the process and results of this invention, the following examples are presented of the soap-removal step for the purpose of illustration, but are not, however, to be taken ab lltniti'ng the scope of the -invention.

The ddllowing examples, re'sults of which :are given in the table below, were conducted as follows:

'In each or the 5 experiments summarized in the followi'ng table, a 500cc. sample of :an alkalitart-rated, straight-"run distillate -from a California brude'oil having an imitial'boiling point :of 881 F. a'nd anend point of'720 F.1and a soap number of 020356, was m'ix'ed with an aqueous surfaceactive solution in a separatory funnel for five minutes "and 'then "allowled to stand :for twenty minutes -=in order to obtain :a :phase separation. Theaqueousmhase was drawn off and the soap number 0f the treated 'oil 'was determined. In -each-of the tests, the surface-.activeagent was a sodium 'alkyl 'aryl isulfonate -having :an average molecular weight of about 350.

Summary of results Test f Treatment Soap No.

;1. one 0.0356 1 =50 ccioi0.026-Wt percent of-surlace-active 0. 005

gsolutiou.

100 cc. of 0.026 wt. percent of surface-active. .0. 004

solution. 150.com 0.026-wt. percent oi surface-active 10.002

solution. I v 250cc; M05026 wt. percent ol'surfacemctlve Nil u n 50cc. of 0.005 wt..percent of surface-active solution. 100 cc; 050005 wt.;percefit obsurface-active 0. 005

solutlQu. v 150001- 01 0.005 wt: percent of suriacesctlye 0:003 solution. v} I j .250 cc. of 0.005wt. percent of surface-active 0.001 solution. 50 cc.-;of 0.10 -wt. percent of surface-active 02001 solution. v v 100 60; of 0.10 wt. percent of surface-active Nil solution, 150cc. M010 wt; percent of surface-active Nil solutio'n.

As illustrated by Example 6 of 'the foregoing tablejlt can be seen that 'a very "small amount 8 of surface-active agent removes substantially all of the soap from the oil. I

1. A process of producing diesel fuel oils and soaps of naphthenic'acids from the naphthenicacid containing petroleum hydrooarbon tr-actions boiling within the range of about 325 to about 725 which comprises washing the hydrocarbon fractions with an aqueous caustic solution whereby the :naphthenic acids, are converted to the per-- =responding soap, settling the 'washed imixture separating the resultant hydrocarbons and agile-- ous phase containing derived .naphthenic esoazps; washing the separated hydrocarbons with :an :aqueous solution consisting essentially lQf water and 0.001 to about 0.1 weight per cent :of i311 iailkyl aryl sulfonate having an average molecular weight of about 350 one volume ratio 10f saidhydrocarbons'to 'said aqueous solution of about 1:1 -to about 20:1; and settling the washed mixture and ='separating :an aqueous :phase containing nap'hthenic soaps and resultant .naphthenic-soap free "diesel -fuel oil.

2. A process "of producing fuel oils :and soaps of :naphthenic acids from naphthenic-pacid containing petroleum hydrocarbon xfractions boiling within the range of about 325 to about 2800 F. which comprises treating the hydrocarbon fractions with an aqueous alkali solution whereby the naphthenic acids are converted to "the corresponding soaps, separating the treated hydrocarbon and aqueous alkali solution :containing naphthenic f soaps; treating the separated hydrocarbons with a dilute aqueous solution consisting essentially of water and la water+so1uble,"alkyl aromatic sulfonate; and separating an aqueous phase containing said naphthenic :soaps from "a resulting petroleum hydrocarbon phase.

3. A process of producing :fueloilsandasoaps of naphthenic acids :irom naphtheniceacid 'containing petroleum hydrocarbon fractions zboiling within-the range of about 325 to'about 800irF. which comprises treating the hydrocarbon :fractions with :an aqueous alkali solution whereby the naphthenio acids are converted to the :corresponding :soaps; separating the treated hydroicarbon and aqueous alkali solution -contain'ing naphthenic soaps treating the separated hydrocarbons with a dilute aqueous solution consisting essentially of water. andsa watei soluble alkyl benzene sulfonate; and separating an aqueous phase containing said naphthenic isoaps from a resulting petroleum hydrooarbonrphase.

CYRIL R. .TURNER.

References I'Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2232,11? Kyrioles Feb. 18, 1941 2,315,766 .Border Apr. 6, 1943 -2 ',346,497 .Lovll Apr. All, 19% 2,413,161 Zerneret al. Dec. 2.4, 19.46 "2,439,670 'Oosterhout Apr. ,13, 1948 2520,407 Hughes .-Al1 g..29, .1950 2,527, 76 iCohen O ct. '2 l, 1950 

1. A PROCESS OF PRODUCING DIESEL FUEL OILS AND SOAPS OF NAPHTHENIC ACIDS FROM THE NAPHTHENICACID CONTAINING PETROLEUM HYDROCARBON FRACTIONS BOILING WITHIN THE RANGE OF ABOUT 325 TO ABOUT 725* F. WHICH COMPRISES WASHING THE HYDROCARBON FRACTIONS WITH AN AQUEOUS CAUSTIC SOLUTION WHEREBY THE NAPHTHENIC ACIDS ARE CONVERTED TO THE CORRESPONDING SOAP, SETTLING THE WASHED MIXTURE AND SEPARATING THE RESULTANT HYDROCARBONS AND AQUEOUS PHASE CONTAINING DERIVED NAPHTHENIC SOAPS; WASHING THE SEPARATED HYDROCARBONS WITH AN AQUEOUS SOLUTION CONSISTING ESSENTIALLY OF WATER AND 0.001 TO ABOUT 0.1 WEIGHT PER CENT OF AN ALKYL ARYL SULFONATE HAVING AN AVERAGE MOLECULAR WEIGHT OF ABOUT 350 IN A VOLUME RATIO OF SAID HYDROCARBONS TO SAID AQUEOUS SOLUTION OF ABOUT 1:1 TO ABOUT 20:1; AND SETTLING THE WASHED MIXTURE AND SEPARATING AN AQUEOUS PHASE CONTAINING NAPHTHENIC SOAPS AND RESULTANT NAPHTHENIC-SOAP FREE DIESEL FUEL OIL. 